146 Shaw — Structure of the Flowers in 



that the aerial cleistogamic flowers are developed among the 

 green foliage, fairly sets aside also any question of their being 

 a contrivance for protection against herbivorous animals. 



There is one fact in connection with cleistogamic flowers in 

 general, which it does not seem to the writer has been prop- 

 erly taken into account in theories concerning such. I refer 

 to the rapidity with which the seeds are matured from them. 

 In Polygala polygavia, much less time is required to produce 

 seed from the cleistogamic flowers, than for the maturing of 

 seed from the evident flowers. The same is true of other 

 plants. In AmphicarpcEa, for instance, the development of 

 fruit from the cleistogamic flowers is relatively rapid. Some 

 reason must lie back of this phenomenon. It would seem that 

 a cleistogamic flower, requiring a minimum expenditure of 

 material, leaves the shoot prepared to furnish the food very 

 rapidly for the maturing of fruit. Here, as in many other 

 points, Darwin's suggestion after the lapse of years proves the 

 soundest. Cleistogamic flowers are economical in the amount 

 of food required to form the flower parts, and especially in 

 the production of pollen. 



Although the observ^ations of Hansgirg, Kerner and 

 Schively leave no room to doubt that light has an influence 

 on the development of the conspicuous parts of blossoms, 

 and even a determining influence on the nature of the flower, 

 as Vochting demonstrated in Linaria spuria, yet these leave 

 the explanation of cleistogamic flowers still incomplete. 

 Some other cause or purpose must exist for the habitual 

 development, under favorable conditions of such numbers of 

 aerial cleistogamic flowers as are put forth by Polygala 

 polygama in the sunny weeks of summer. 



Considering the rapidity with which the fruits are matured, 

 it seems to the writer that the explanation is chiefly to be 

 found in the relation of cleistogamic flowers to the chas- 

 mogamic ones in the matter of food supply. 



